From the looks of the arm, it seems like you can't move the head to all points on a plane parallel to the table without refocusing. This seems inconvenient for big boards that are clamped down for soldering.

From the looks of the arm, it seems like you can't move the head to all points on a plane parallel to the table without refocusing. This seems inconvenient for big boards that are clamped down for soldering.

That is a limitation of the cheaper mantis units. You basically get an arc of coverage on the bench, with only a small change in radius with up/down to focus. In practice this isn't a big problem as that thing you are looking at can be moved into the working area. They do make some fancier arms if you really need more flexibility.